Standard cell construction



F. w. SIDE 2,484,593

STANDARD CELL CONSTRUCTION 2 Sheets-Sheet 1 Filed Aug. 15, 1946 FIG.|

INVENTOR.

. FREDERICK W. SIDE ATTORNEY.

Get, 11 E, 1949.

STANDARD CELL CONSTRUCTION Filed Aug. 15, 1946 2 Sheets-Sheet 2 ll Cd S0 8 Mercury P-Cadmium Amalgam 7 INVENTOR. FREDERICK W. SIDE ATTORNEY.

F. w. SIDE 25484593 Patented Oct. 11, 1949 2,484,593 STANDARD CELL CONSTRUCTION Frederick w. Side, Philadelphia, r assignor, by mcsne assignments, to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application August is, 1946, Serial No. 69011 92 Claims. (Cl. 186-88) The present invention relates to primary cells and more particularly to standard cells of the Weston type which are used as voltage standards in potentiometric work.

Standard cells are used extensively for calibration purposes in potentiometers which are used for measuring small voltages accurately. For this purpose the output of the cell should not vary. It is known, however, that the output of the cell will change if the temperatures of the two legs of a conventional H-shaped cell are varied even a small amount. When using these cells in a potentiometer instrument, for example, it is frequently necessary, because of space or construction limitations, to mount them adjacent a heat producing device such as a motor. Unless extreme care is used one leg of the cell is likely to be nearer the motor than the other leg with a consequent increase in temperature of the first leg with respect to the second. This means that the voltage of the cell will vary from its standard, calibrated value. Another difiiculty with the presently obtainable standard cells is that their size is such that they require more space than is often readily available in modern potentiometer instruments.

It is an objector the present invention to overcome the above mentioned difliculties by making a standard cell that is small in size'and one that has its twolegs joined by a temperature equalizing portion. Ordinarily the internal resistance of a standard cell varies directly with the distance between the two electrodes and inversely with the area of the legs. present invention the reduction in area of the legs is substantially compensated for by the shortening of the distance between the electrodes.

Thus, the present cell, in spite of its small size, has an internal resistance that is not appreciably larger than that of the larger commercially available types that are in general use today.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages, and specific objectsattained with its use,

reference should be had to the accompanying drawing and descriptive matter in which I have illustrated and described preferred embodiments of the invention.

In the drawings:

Figure 1 is a view of the standard cell, and

Figure 2 is a view taken on line 22 of Figure 1.

Figure 3 is a vertical longitudinal cross section on line 3-3 of Figure 2.

The standard cell of this invention comprises a glass tube l which has had its lower portion formed into two legs 2 and 3 which are joined by In the cell of thea flange or web of glass 4. Preferably the cell blank starts out as a closed end glass tube, such and the blank was originally a tube the glass extending between the legs forms a flange or web between the legs. This is a highly desirable feature since it serves both to strengthen the cell blank and to form a temperature conductin connection between the legs of the cell.

After the cell blank has been made the various chemicals are placed in the blank. A body oi cadmium amalgam l is placed in the bottom of the negative leg 3 in good electrical contact with the platinum electrode 5. This cadmium amalgam is formed by mixing mercury and cadmium. The mixture is heated so that it becomes sufliciently fluid to be poured into the bottom of the negative leg 3. As shown at'8 a body of pure mercury is placed at the bottom of the positive leg 2. Above this mercury in leg 2 is placed mercurous sulphate paste 9. An amount of electrolyte H, which is a solution of cadmium sulphate, is then poured into the blank above the solid ingredients to a level even with the top of the legs 2 and 3. In order to maintain the amalgam and the mercurous sulphate in the cell legs it is customary to employ some type of dam or baffie. In this case small corks l2 and I3, that are provided with suitable apertures in their centers as is shown in Figure 2, are placed one in each leg of the cell above the solid ingredients. It is not ncessary that the cork be in engagement with these ingredients so long as it is tight enough to stay in place as the cell is tilted in transportation or use. In some cases it may be desirable or necessary to provide a linen washer ill around the corks in order to hold them tightly in place and in order to provide a dam or barrier across the openings that are provided therein. This may be accomplished by merely forming a disk of linen in a slightly cupped shape so that when the cork is moved intoplace the linen will be carried in with it. The linen washer will be engaged on both sides by the electrolyte so that it will not have any efiect on the ion path during the operation of the cell. When the corks are in place the remainder of the electrolyte is placed in the cell to a level sufiicient so that the finished cell may be laid on itsside and still have the electrolyte bridge the legs. When the various chemical ingredients are in place the upper end of the cell blank can be heated and sealed off above the level of the electrolyte as is shown at l5. It is noted that cells made in accordance with the present invention have a total length of approximately two and one-half inches and a diameter 01 approximately three-quarter inch. Each of the ameter and approximately flve-eighths inch long. A cell of the type described above has many Because of the fact .that the cell can. be moved to various positions-and stfll have its electrical path closed it is possible to use a cell of this type in portable instruments wherein they have never advantages not the least of which is its small 5 before been used. 7 H size. In a study of this type. of cell it has been While in accordance with the provisions of the determined the size of the cell and the amount statutes, I have illustrated and described the best of the chemical ingredients used in its manuforms of the invention now known to me, it will facture have no eflect on the voltage which it be apparent to those skilled in the art that produces, A cell of this type will produce, when 10 changes may be made in the form of the apparaproperly manufactured, exactly the same voltage tus disclosed without departing from the spirit which is produced by the conventional shape of the invention as set forth in the appended large size standard cells of the Weston type. claims, and that in some cases certain features It is known that the internal resistance of a v of the invention may sometimes be used to adstandard cell varies directly with the distance vantagewithout a corresponding use of other between the electrodes and inversely with the features. 7

area of the legs. This fact has been to some ex- Having now described my invention, what I tent a controlling feature in the size of commerclaim as new and desire to secure by Letters Pat cially available standard cells. If the convenent is: tional. H-shaped blank is made in smaller size 1. Astandard cell consisting of a closed tubular the internal resistance of the cell increases to body formed at its lower end withapair of tubular almost prohibitive values. With the cell of the legs, said legs being joined with a heat-conductpresent invention, however, the disadvantage of mg flange, and an electrode inserted in each leg. the small diameter legsis substantially over- 2. A standard cell consisting of a closed tubular. come by the very short ion path between the two glass .body, a pair of tubular glass legs extending electrodes. An additional advantage of the side by side from one end of said body and inpresent cell over the conventional H-shaped cell, egral and in communication therewith, said legs and particularly, a small one, is the simplified being joined by a flange, and an electrode extend-' glass forming operation that is required. ing from each leg.

It has been known fora long time that the 3 3. A standard cell comprising a closed one piece voltage output of a standard cell varied considert ul r glass body, a pair of glass legs unitary ablywhen the legs ofthe cell were at different th said body and extending from said body emp ra ures C eq y these cells must e in side by side relation and having a total area so mounted that they are not in draf n 50 less than that of said body, and a' flange of glass that y a e not located too near a heat p d joining said legs throughout their entire length ing body. If t s i done o e leg is e y o get 4. A standard cell comprising a closed tubular hotter than the other and the cell can no longer glass body having'a pair of integrally formed legs be sed for Standardizing purposes- The reason projecting from one end thereof, said legs each for this is that the positive or mercurous sulphate being of a smaller diameter than said body. a eg o the Cell has a p t temperature eoeffl- 40 body of cadmium amalgam in one leg, a perforated cient while the amalgam leg has a negative temdam in said leg above said amalgam, a body of perature coefficient. 'I'hese two coeflicients are mercury in the other leg, a body of mercurous substantially'the sameand will 'efiectively offset sulphate in said other leg above said mercury, a each other if the temperature of the cell as .a perforated dam in said other leg above said merwhole is raised or lowered within reasonable limcurous sulphate, an electrolyte of a solution of its. This particular defect in the conventional cadmium sulphate-filling the remainder of said standard cell is eflectively .overcome by the conlegs and a portion of said body; a glass flange construction of the present cellsincexthe two legs of necting said legs, an electrode extending through the cell are close together andjoined by theiheat one leg into contact with saidcadmium sulphate,

conducting flange 4' which extends'between'them. 0 and anfelectrode extending through the'other leg Due to the small'size of the cell :and' the heat con-* into contact with said mercury. I

' ducting capacity of-theglass the chancesof one 5. A standard cell cdmprising a closed tubular leg of the cell being at a different temperature "body having a'homogenous portion forming a pair than the other leg are inconsequential. of legs-extending from one end of said body, a

' In the conventional standard cell enough .elec-' flange joiningv said-legs, an electrode extending of the H andthe lower .halfof each of the legs trolyte must'be used "so that .the cross member from each leg, and chemically active voltage'producingmaterial in said legs an a porfidn 15am: j areconnecte'din.anelectricaipath. The amount i v that one of these cells canbe moved out of "the r vertical is limitedby the amount of electrolyte that can be placed in the cell.

which is placed in the'upper. part of the 'cell blank is sumcieh'tsothat'thecellmay beoperative-even With a constructionof the type disclosedherein the electrolyte pr nces on file of patent:

when. it is laicbon its'side. The ability-"to form 6 i STATES P? a cell in which its operative position "is not critical Number Name e 4 is of grea importance. 1,528,076 I Rodman et a1. Mar. 3, 1925 From the above description it will be seen that 1,387,531 w .1 15 1932 this. invention is directed to a novel type of conf y struction to be'used for a standard cell. The cell i OTHER BEFERENCES produced is one whose usefulness is not limited to a constant temperature location or to a location in which the position of the cell is critical.

Fleming, Centralblatt fur'E lectrotechnik, vol. 8, No. 32 1886), page 712.

' following references are of record in'the 

